JP2010190279A - Poppet check valve for travel unit counter balance valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a poppet check valve for a travel unit counter balance valve avoiding a problem such as cavitation by improving oil suction performance to a hydraulic motor inlet part during vehicle stop operation. <P>SOLUTION: This poppet check valve for the travel unit counter balance valve is installed between a hydraulic motor side channel and a hydraulic pump side channel in a brake valve body of a brake valve 50. A poppet inlet of the poppet check valve is connected to the hydraulic pump side channel. A poppet outlet is connected to the hydraulic motor side channel, and is provided with a communication path opening to a connection part where the hydraulic motor side channel communicates with a channel of the hydraulic motor 20 at one end and opening to a poppet back surface chamber of the poppet check valve at another end. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a poppet check valve for a counter balance valve of a brake valve used in a traveling unit such as a hydraulic crawler vehicle.

  If the supply pressure to the hydraulic motor is reduced when the traveling unit of the hydraulic vehicle is stopped, the counter balance valve of the brake valve returns to neutral, thereby stopping when the oil discharged from the hydraulic motor is shut off. During this stop operation, the hydraulic motor performs a pumping operation with inertia, and the hydraulic motor outlet pressure becomes high, but the brake valve crossover relief valve (hereinafter also simply referred to as “relief valve”) is blown, thereby causing inertia. By making the energy heat, the hydraulic motor is given a braking force. The blown oil passes through the relief valve downstream and is supplied again to the inlet of the hydraulic motor. The hydraulic motor sucks this oil until the stop operation is completed and blows the relief valve, generating an oil circulation flow. Let Such a hydraulic drive device for a traveling unit incorporating a relief valve for a brake valve is disclosed in, for example, Japanese Patent Application Laid-Open No. 8-296604 (Patent Document 1). The traveling unit includes a reduction gear 10 part, a hydraulic motor 20 part, and a brake valve 50 part shown in FIGS.

  Hereinafter, an example of a conventional hydraulic unit for a traveling unit of a vehicle will be described with reference to FIGS. 4 and 5. 4 shows the vehicle in a stopped state, and FIG. 5 shows the traveling state. 4 and 5 are flow diagrams of the hydraulic oil of the traveling unit. In FIGS. 4 and 5, the relief valve 70, the counter balance valve 60 and the poppet check valve (hereinafter simply referred to as “check valve”) constituting the brake valve 50. 65 "indicates one individual cross section, and does not indicate the entire three-dimensional configuration. Also, white arrows in FIG. 4 indicate the oil flow (circulation flow) during the stop operation, and black arrows indicate the oil flow supplied from the check valve during the stop operation. The arrows in FIG. 5 indicate the flow of oil during travel. In addition, the flow path shown with a dashed-two dotted line in FIG. 4 is the communicating path 165j added in this invention mentioned later.

  4 and 5, reference numeral 30 denotes a hydraulic pressure source, for example, a hydraulic pump 31 driven by an internal combustion engine to send out high-pressure hydraulic oil, a hydraulic pressure relief valve 32 for releasing an overpressure of hydraulic pressure from the hydraulic pump 31, a reservoir (Oil tank) 33 and the like. A control valve 40 is connected to the flow paths K and M of the brake valve 50 by switching the reciprocating flow path from the hydraulic power source 30 to normal rotation, neutral and reverse rotation according to a command from a control device (not shown). In the brake valve body 52 of the brake valve 50, a set of counter balance valves 60 and two sets of relief valves 70R and 70L are provided. The counter balance valve 60 is provided with a spool 64, check valves 65R and 65L, springs 67R and 67L, and the like. The check valves 65R and 65L are usually constituted by poppet type check valves. In addition, R and L attached | subjected to each number are what attached | subjected R to the thing of the right side in FIG. To do.

As shown in FIGS. 4 and 5, the relief valves 70 </ b> R and 70 </ b> L are oil-tightly screwed into the brake valve body 52 in which the flow paths R and L in the brake valve 50 are formed. The flow path L and the flow path R are separated by bringing the tip of the relief valve 70 into close contact with one of the flow paths R and L where the branch flow paths Ld and Rd of the other flow path are connected. Is formed. As shown in the figure, the relief valve 70R is assembled so that the branch flow path Ld of the flow path L hits the tip of the relief valve 70R and the flow path R is in contact with the outer periphery of the tip of the relief valve 70R. The relief valve 70L has the same structure with the flow paths R and L reversed.
When an overload pressure is generated in the flow path L, the relief valve 70R releases the overload pressure from the branch flow path Ld to the flow path R (blowing the relief valve 70R). When an overload pressure is generated in the flow path R, the relief valve 70L releases the overload pressure from the branch flow path Rd to the flow path L (blowing the relief valve 70L).

Next, the operation of the hydraulic apparatus shown in FIGS. 4 and 5 will be described. As shown in FIG. 4, when the control valve 40 is set to the neutral position, both the flow path K and the flow path M are communicated with the return pipe 34 and no pressure is applied. The spool 64 of the counter balance valve 60 is in a neutral position by both springs 67R and 67L, the flow paths R and L are shut off, respectively, and are also shut off by the non-actuated check valves 65R and 65L. Do not flow freely. This is to prevent such a situation because if the oil freely enters and exits the hydraulic motor 20, the vehicle may move freely due to external force, ground inclination, or the like. The counter balance valve 60 and its check valves 65R and 65L have a meter-out structure in which the flow from the outlet of the hydraulic motor 20 is closed but the flow to the inlet of the hydraulic motor 20 is communicated.
In the stop state, the spring-operated parking brake 11 is operated as shown in the figure.

In the running state, for example, in the right position of the control valve 40 shown in FIG. 5, the hydraulic pressure enters the flow path K, the spool 64 is pushed from right to left, and the pressure oil flows from the flow path K as indicated by the arrow on the flow path. It flows in the path R, flows from the right to the left of the hydraulic motor 20 and is driven to rotate, flows from the flow path L to the flow path M, and returns to the reservoir 33. Although not shown, at the left position of the control valve 40, oil flows in reverse, and the hydraulic motor 20 is rotationally driven in a direction opposite to the direction of FIG.
In the running state, as shown in the figure, the spring-operated parking brake 11 is released by hydraulic pressure.

When the traveling vehicle is stopped, that is, when the control valve 40 at the right position is moved from the traveling state shown in FIG. 5 to the neutral position shown in FIG. Operation occurs.
Both the flow paths K and M are connected to the return pipe 34 so that no pressure is applied. The spool 64 of the counter balance valve 60 is in the center position due to the balance between the spring 67R and the spring 67L, and the check valves 65R and 65L of the counter balance valve 60 are set. Closes the flow paths R, L. On the other hand, the hydraulic motor 20 causes the pumping action to rotate as usual due to the inertial force of the movement of the vehicle body and other masses, and tries to flow oil from the flow path R to the flow path L through the hydraulic motor 20. However, since the flowing oil is suddenly stopped, a high pressure is instantaneously generated in the flow path L and a negative pressure is generated in the flow path R.

When the high pressure generated in the flow path L is applied from the branch flow path Ld to the relief valve 70R and exceeds the relief pressure, the relief valve 70R blows (the high pressure oil from the relief valve 70R to the branch flow path Ld is low pressure flow path R The oil that has entered the flow path R from the branch flow path Ld is sucked into the inlet of the hydraulic pump 20. Therefore, as shown in the circulation flow indicated by the white arrow in FIG. 4, the hydraulic motor 20 performs the operation of sucking this oil and blowing the relief valve 70R until the stop operation is completed.
The parking brake 11 is operated with a delay after the stop operation.

As described above, when the vehicle is stopped, a circulating flow is generated through the relief valve 70 during the pumping action of the hydraulic motor 20, and during that time, the hydraulic motor 20 increases the braking force by heating the inertial energy. However, during the stop operation, oil leaks from the clearance of the counter balance valve 60 that is about to close, so that 100% of the oil discharged on the outlet side of the hydraulic motor 20 blows the relief valve 70 and the inlet of the hydraulic motor 20 It is not supplied to the side.
At this time, if there is a lot of leakage at the outlet side of the hydraulic motor 20 and the supply oil returning to the inlet side of the hydraulic motor 20 is insufficient, a negative pressure is generated at the inlet of the hydraulic motor 20 and problems such as cavitation occur.

Therefore, conventionally, in addition to the oil returning from the relief valve 70, oil is also supplied through the check valve 65 as indicated by the black arrow from the check valve 65R in FIG. FIG. 1 shows a cross section of the check valve 65 as viewed in the direction of arrows XX in FIG. 4. The left half of FIG. 1 is a conventional check valve 65, and the right half of FIG. 1 is a check valve 165 according to the present invention described later. .
As shown in the left half of FIG. 1, the brake valve body 52 of the brake valve 50 having the check valve 65 is attached to the valve disc 21 of the hydraulic motor 20, and the poppet 65 a is not operated in the brake valve body 52. The motor-side flow channel 66b of the flow channel 66 to be closed (the flow channels K and R in FIGS. 4 and 5 or the flow channels M and L) opens to a connection portion 66c that communicates with the valve plate flow channel 21a of the valve plate 21. ing.

The poppet 65a of the check valve 65 has a communication hole 65c that is drilled in the head 65b of the poppet 65a and communicates with the motor-side flow channel 66b, and a back hole 65e that communicates the hole 65c and the poppet back chamber 65d. .
Therefore, the communication hole 65c and the back hole 65e allow oil to flow into and out of the poppet back chamber 65d, so that the operation of the poppet 65a is not hindered. When a negative pressure is generated in the flow path on the inlet side of the hydraulic motor 20 (flow path R in FIG. 4) by approaching the pressure of the pressure, the pressure in the poppet back chamber 65d is reduced in the flow path 66 facing the poppet inlet 65f. The poppet 65a is operated against the poppet spring 65g so that the pressure is lower than the pressure of the pump side channel 66a, and the oil flows from the pump side channel 66a to the motor side channel 66b. The oil supply to 20 was supplemented.
Further, instead of the communication hole 65c and the back surface hole 65e, a communication groove 65i (see FIG. 2) is provided in the axial direction of the outer surface of the poppet 65a ', and the motor side flow channel 66b and the poppet back chamber 65d are communicated with each other. There was also a check valve 65 'obtained.

However, in the check valve 65 including the poppet 65a as described above, as described later,
The difference between the pressure at the poppet inlet 65f and the pressure at the poppet back chamber 65d is small, and it is difficult to stably maintain the opening of the check valve 65 against the poppet spring 65g. Therefore, there is a possibility that a negative pressure is generated on the inlet side of the hydraulic motor 20 to cause problems such as cavitation.

  This is because the poppet type check valve 65 facilitates the inflow of oil into the hydraulic motor 20 and prevents backflow, and the high pressure (primary pressure) of the pump side flow path 66a applied to the poppet inlet 65f. It is a mechanism that reacts and opens, and is not a mechanism that reacts to the low pressure (secondary pressure) of the motor-side channel 66b applied to the poppet outlet 65h, but the secondary pressure becomes low (negative pressure) when the vehicle is stopped. However, the reaction of the poppet 65a is poor, the oil is not supplied from the hydraulic pump 31, and the primary pressure is also lowered. Therefore, it is difficult to open the poppet, and in response to this, the communication hole 65c and the rear hole 65e as described above. Or the communication groove 65i guides the secondary pressure into the poppet back chamber 65d, but once the poppet 65 is opened and oil flows, the motor side flow path applied to the poppet outlet 65h. The pressure 6b (secondary pressure) becomes higher than the pressure in the vicinity of the valve plate 21 due to the flow resistance of the motor side flow channel 66b, and the low pressure (negative pressure) generated in the vicinity of the valve plate 21 remains in the poppet back chamber 65d as it is. This is because it does not work.

JP-A-8-296604 (pages 3-5, FIGS. 1-4)

  The present invention eliminates the problems of the conventional vehicle traveling unit described above, improves the oil suction performance to the hydraulic motor inlet during the stopping operation of the vehicle, and avoids problems such as cavitation and the like. It is an object to provide a poppet check valve for use.

  The present invention has been made to solve the above problems, and provides the following means (1) and (2), which will be described in the order of the claims.

  (1) As a first means, there is a poppet check valve for a counter balance valve of a traveling unit interposed between a hydraulic pump side flow passage and a hydraulic motor side flow passage in a brake valve body of the brake valve. The poppet inlet of the poppet check valve is connected to the hydraulic pump side flow path, the poppet outlet is connected to the hydraulic motor side flow path, and one end of the hydraulic motor side flow path communicates with the flow path of the hydraulic motor. There is provided a poppet check valve for a counter balance valve of a traveling unit, characterized in that it is provided with a communication passage that opens to a connecting portion and the other end opens to a poppet back chamber of the poppet check valve.

  (2) As a second means, in the counter balance valve poppet check valve of the traveling unit of the first means, the hydraulic pressure comprising the hydraulic pump side flow path and the hydraulic motor side flow path is provided in the brake valve body. A reciprocating flow path for the motor, a set of counter balance valves interposed in the reciprocating flow path, the poppet check valve of the counter balance valve interposed for each of the reciprocating flow paths, A relief valve interposed in the reciprocating flow path, and the relief valve is configured to release an overload pressure generated in one of the reciprocating flow paths to the other of the reciprocating flow paths. A poppet check valve for a counter balance valve of a traveling unit is provided.

  (1) According to the first aspect of the present invention, since the poppet check valve for the counter balance valve of the traveling unit is configured as the first means, the inlet-side flow path of the hydraulic pump Since the pressure is guided to the poppet back chamber via the communication path, the poppet easily operates and opens in response to a decrease in the suction pressure on the inlet side of the hydraulic pump, and the pressure in the poppet back chamber remains hydraulic after opening. Since the pressure in the flow path on the inlet side of the pump is maintained, the operating state of the poppet is stable, and oil can be stably supplied from the flow path on the hydraulic pump side to the flow path on the hydraulic motor side via the poppet check valve. The Therefore, it is possible to prevent problems such as cavitation due to generation of negative pressure due to insufficient supply oil on the hydraulic pump inlet side.

  (2) According to the invention of claim 2 of the claims, the poppet check valve for the counter balance valve of the traveling unit is configured as the second means, so that the effect of the invention of claim 1 is achieved. In addition, during the stopping operation of the traveling unit, the hydraulic motor performs a pumping operation with inertia, the outlet pressure of the hydraulic motor becomes high, the relief valve blows, and the blown oil passes again downstream of the relief valve to the inlet side of the hydraulic motor again. The hydraulic motor generates a circulating flow of oil until the stop operation is completed.If the oil pressure at the inlet of the hydraulic motor is insufficient and the pressure drops, the poppet check valve reacts immediately. Therefore, it is possible to stably supply the oil, so that problems such as cavitation on the inlet side of the hydraulic motor can be prevented.

FIG. 5 is a longitudinal sectional view of the counter balance valve poppet check valve of the traveling unit according to one embodiment of the present invention, as viewed in the direction of arrows XX in FIG. 4, and the right half of FIG. The half shows the corresponding conventional example. It is a typical longitudinal cross-sectional view for description of a pressure relationship and operation | movement of the poppet check valve for counter balance valves of the traveling unit of a prior art example, (a) is the example, (b) is another example. It is a typical longitudinal cross-sectional view for description of a pressure relationship and operation | movement of the poppet check valve for counter balance valves of the traveling unit of a present Example. It is explanatory drawing of the hydraulic device of the traveling unit of the vehicle which has a brake valve provided with the conventional poppet check valve for counter balance valves, and shows the stop state of a vehicle. It also serves as an explanatory diagram of application of the embodiment of the present invention. It is explanatory drawing of the hydraulic device of the traveling unit of the vehicle which has a brake valve provided with the conventional poppet check valve for counter balance valves, and shows the traveling state of the vehicle.

  As an embodiment for carrying out the present invention, an embodiment will be described below.

A poppet check valve for a counter balance valve of a traveling unit according to an embodiment of the present invention will be described with reference to FIG.
FIG. 1 shows a longitudinal section of a check valve as viewed in the direction of arrows XX in FIG. 4, the left half of which shows the above-described conventional check valve 65, and the right half of which is a check valve according to an embodiment of the present invention. 165 is shown. As shown in the right half of FIG. 1, the poppet 165a of the check valve 165 of the present embodiment has a communication hole 65c, a back surface hole 65e, a communication groove 65j (see FIG. 2) is not provided.

  The brake valve body 52 of the brake valve 50 having the check valve 165 is attached to the valve plate 21 of the hydraulic motor 20. In the brake valve body 52, the motor side flow channel 66 b of the flow channel 66 that is closed when the poppet 165 a is not operated. Is open to the connecting portion 66c communicating with the valve plate flow path 21a of the valve plate 21.

The check valve 165 of the present embodiment has one end opened so as to communicate with the poppet back chamber 165d, and the other end communicated with the motor side channel 66b opened to a connection portion communicating with the valve plate channel 21a of the valve plate 21. A passage 165j is provided in the brake valve body 52.
Therefore, the communication passage 165j allows oil to flow in and out of the poppet back chamber 165d, so that the operation of the poppet 165a is not hindered, and the pressure in the poppet back chamber 165d is brought close to the pressure near the valve plate 21 of the motor side flow channel 66b. It is possible to do.

  Even when a pressure drop (for example, negative pressure) occurs in the flow path on the inlet side of the hydraulic motor 20 (the flow path R in FIG. 4), the valve disc flow on the inlet side of the poppet back chamber 65d and the hydraulic motor 20 in the communication path 165j. Since a substantial flow does not occur between the passage 21a and the pressure in the poppet back chamber 65d through the communication passage 165j is almost the same as the pressure in the valve disc flow passage 21a, the pump facing the poppet inlet 165f is used. The opening of the check valve 165 which is significantly lower than the pressure of the side flow path 66a, and the poppet 165a operates stably against the poppet spring 165g to flow oil from the pump side flow path 66a to the motor side flow path 66b. Is maintained, and the supply of oil to the hydraulic motor 20 during the stop operation described above can be sufficiently supplemented.

  That is, since the pressure in the inlet-side flow path of the hydraulic motor 20 is guided to the poppet back chamber 165d through the communication path 165j, the poppet 165a easily operates in response to a decrease in the suction pressure on the inlet side of the hydraulic motor 20. Since the pressure in the poppet rear chamber 165d is maintained at the pressure in the inlet side flow path of the hydraulic motor 20 even after the opening, the operating state of the poppet 165a is stabilized, and the hydraulic pump sidestream is supplied via the check valve 165. It is possible to stably supply oil from the passage 66a to the hydraulic motor side passage 66b. Therefore, it is possible to prevent the occurrence of problems such as cavitation due to the generation of negative pressure due to insufficient supply oil on the inlet side of the hydraulic motor 20.

  In addition, since the check valve 165 is provided in the brake valve body 52 as described above, the hydraulic motor 20 performs a pumping operation by inertia during the stopping operation of the traveling unit, and the outlet pressure of the hydraulic motor 20 becomes high and the relief is performed. The oil blown through the valve 70 is supplied again to the inlet side of the hydraulic motor 20 through the downstream side of the relief valve 70, and the hydraulic motor 20 generates a circulating oil flow until the stop operation is completed. When the oil pressure in the side flow path is insufficient and the pressure drops, the check valve 165 can react immediately and supply oil stably, so that problems such as cavitation on the inlet side of the hydraulic motor 20 occur. Can be prevented.

Hereinafter, based on FIGS. 2 and 3, a difference in operation effect of the check valve 165 of the present embodiment with respect to the check valve 65 of the conventional example will be schematically described.
FIG. 2A schematically shows a conventional check valve 65 shown on the left half of FIG. In FIG. 2A, Pa is the pressure at the poppet inlet 65f of the check valve 65 of the pump side channel 66a, Pb is the pressure at the poppet outlet 65h of the motor side channel 66b, and Pc is the valve disc flow of the motor side channel 66b. The pressure Pd at the connecting portion 66c with the passage 21a is the oil pressure in the poppet back chamber 65d.

When the check valve 65 is not in operation (closed), there is no flow from the pump side flow path 66a to the motor side flow path 66b, and there is no flow in the motor side flow path 66b.
Pa−Pb is large, Pb = Pc,
Further, since the motor side flow channel 66b of the poppet outlet 65h communicates with the poppet back chamber 65d through the communication hole 65c and the back hole 65e, there is substantially no flow between them.
Pd≈Pb
Therefore, the differential pressure acting on the poppet 65a is
Pa-Pd≈Pa-Pc
When Pc is reduced in pressure, the poppet 65a opens against the poppet spring 65g.

However, once the operation state (opening) is reached, a flow is generated from the pump side channel 66a to the motor side channel 66b.
Pa−Pb is small, Pb> Pc (a pressure difference is caused by the flow path resistance of the motor side flow path 66b).
On the other hand, the motor side channel 66b of the poppet outlet 65h communicates with the poppet back chamber 65d, and there is substantially no flow between them.
Pd≈Pb
Therefore, the differential pressure acting on the poppet 65 is
Pa-Pd≈Pa-Pb <Pa-Pc
As a result, the differential pressure is reduced by the pressure difference due to the flow path resistance of the motor side flow path 66b as compared with the closed state, the differential pressure decreases, and it becomes unstable to maintain the operating state (opening) of the check valve 65.

  The poppet 65a 'of the check valve 65' in FIG. 2B includes a communication groove 65i in the axial direction of the outer surface of the poppet 65a 'instead of the communication hole 65c and the back surface hole 65e, and the motor side flow path of the poppet outlet 65h. 66b and the poppet back chamber 65d communicate with each other, so the relationship between Pa, Pb, Pc, and Pd is the same as that shown in (a), and the operating state (opening) of the check valve 65 'is maintained. Becomes unstable.

FIG. 3 schematically shows the check valve 165 of the present embodiment shown on the right half of FIG. As described above, the check valve 165 of the present embodiment is opened so that one end communicates with the poppet back chamber 165d, and the other end communicates with the valve disc flow passage 21a of the valve disc 21 like the motor side flow passage 66b. The brake valve body 52 includes a communication passage 165j that opens to the connection portion 66c.
Pa, Pb, Pc, and Pd are the pressures at the same locations as in FIG.

When the check valve 165 is inactive (closed), there is no flow from the pump side flow channel 66a to the motor side flow channel 66b, and there is no flow in the motor side flow channel 66b.
Pa−Pb is large, Pb = Pc,
Further, the connecting portion 66c of the valve disc 21 with which the motor side channel 66b communicates with the valve disc flow passage 21a communicates with the poppet back chamber 65d through the communication passage 165j, and there is substantially no flow therebetween.
Pd≈Pc
Therefore, the differential pressure acting on the poppet 165a is
Pa-Pd≈Pa-Pc
When Pc is reduced in pressure, the poppet 165a opens against the poppet spring 165g.

In addition, when in the operating state (opening), a flow is generated from the pump side flow channel 66a to the motor side flow channel 66b.
Pa-Pb is small, Pb> Pc (a pressure difference occurs due to the flow path resistance of the motor side flow path 66b)
However, the connecting portion 66c of the motor side channel 66b with the valve plate channel 21a communicates with the poppet back chamber 165d through the communication channel 165j, and there is substantially no flow therebetween.
Pd≈Pc
Therefore, the differential pressure acting on the poppet 165a is
Pa-Pd≈Pa-Pc
Thus, the differential pressure due to the low pressure Pc is obtained as in the closed state, and the operating state (opening) of the check valve 165 can be stably maintained.

As described above, the check valve 165 of the present embodiment applies a pressure substantially equal to the pressure on the inlet side of the hydraulic motor 20 (the pressure of the valve disc flow path 21a of the valve disc 21) in FIG. Since the poppet 165a is led directly to the poppet back chamber 165d through the communication passage 165j shown in FIG. 5B and the poppet 165a is operated, if the pressure on the inlet side of the hydraulic motor 20 decreases during the stop operation (negative pressure), As shown by a black arrow in FIG. 4, the pump side flow path 66a (flow path K in FIG. 4) is stably supplied to the motor side flow path 66b (flow path R in FIG. 4) via the check valve 165. Until the hydraulic motor 20 stops, the circulation flow indicated by the white arrow in FIG. 4 can be maintained, and problems such as the occurrence of cavitation on the inlet side of the hydraulic motor 20 can be prevented.
Further, the structure does not add a special mechanism as compared with the conventional structure, and a structure that exhibits the above-described effects can be obtained by a simple partial structure change.
In FIG. 4, the case of the check valve 165R in the case where a low pressure (negative pressure) occurs on the flow path R side has been described, but the case of the check valve 165L in the case where a low pressure (negative pressure) occurs on the flow path L side is also quite complete. The check valve 165 itself has the same structure.

  The present invention has been described with reference to the illustrated embodiment. However, the present invention is not limited to the above-described embodiment, and various modifications may be made to the specific structure and configuration within the scope of the present invention. Not too long. For example, the present invention can be applied not only to the case where the relief valves are provided in the reciprocating passages R and L as described above, but also to the case where a relief valve is used to perform the relief action of both the reciprocating passages R and L with one relief valve. .

  The counter balance valve poppet check valve of the travel unit of the present invention is not limited to the travel unit, and the counter balance valve of the hydraulic drive unit is required to prevent the occurrence of cavitation on the hydraulic motor inlet side during the stop operation, as with the travel unit. It can be used effectively as a poppet check valve.

20 Hydraulic motor 21 Valve board 21a Valve board flow path 30 Hydraulic source 31 Hydraulic pump 40 Control valve 50 Brake valve 52 Brake valve body 60 Counter balance valve 64 Spool 65, 165 Check valve (poppet check valve)
65a, 165a Poppet 65b, 165b Head 65c Communication hole 65d, 165d Rear chamber 65e Back hole 65f, 165f Poppet inlet 65g, 165g Poppet spring 65h, 165h Poppet outlet 65i Communication groove 66 Channel 66a Pump side channel 66b Motor side channel 66b Path 66c Connection section 67 Spring 70 Relief valve 165j Communication path

Claims (2)

  A poppet check valve for a counter balance valve of a traveling unit interposed between a hydraulic pump side flow path and a hydraulic motor side flow path in a brake valve body of the brake valve, wherein the poppet inlet of the poppet check valve Connected to the hydraulic pump side flow path, the poppet outlet is connected to the hydraulic motor side flow path, one end is open to the connection portion where the hydraulic motor side flow path communicates with the flow path of the hydraulic motor, and the other end is A poppet check valve for a counter balance valve of a traveling unit, characterized in that a communication passage opening in a poppet back chamber of the poppet check valve is provided.   The poppet check valve for a counter balance valve of the traveling unit according to claim 1, wherein a reciprocating flow path for the hydraulic motor including the hydraulic pump side flow path and the hydraulic motor side flow path is provided in the brake valve body. A set of counter balance valves interposed in the reciprocating flow path, the poppet check valve of the counter balance valve interposed for each of the reciprocating flow paths, and the reciprocating flow path. And a relief valve poppet for a counter balance valve of a traveling unit, wherein the relief valve is configured to release an overload pressure generated in one of the reciprocating flow paths to the other of the reciprocating flow paths. Check valve.

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